Since we call it the Swashbuckler-Artificer it is pretty obvious what our two main classes are. The Swashbuckler has often been called a 3-level class, and it's true. Of course we want the Int bonus to damage, everything else is not so important.

After the 3 levels of Swashbuckler are in, it's Artificer till the end. There is not really a prestige class that helps being a melee artificer, so why bother.

Since no race has Artificer or Swashbuckler as favored class, there is pretty much only the human to play this, unless you want to add more Swashbuckler levels (nah), or your group has done what should have been done by the 3.5 edition authors and thrown out that multiclassing XP penalty crap.

In that case, you may think about:

Halfling

Small size means bonus to attack and AC (great), and +1 to all saves doesn't hurt either. Add +2 to one of the two main abilities.

The down size, small weapon damage and low strength, is made up by the Swashbuckler levels and weapon enhancements

Lesser Tiefling

It's unlikely that a DM will allow Races of Faerun and an Artificer in one campaign, but if he does, you have a good choice here. +2 Int and Dex is right your main abilities.

If LA buyoff is used, the LA+1 tiefling is worth a consideration, too.

With Weapon Finesse for free, it's pretty much settled that you want to use finessable weapons. There are several ways to do it:

rapier and buckler (classic)

two short swords with TWF

spiked chain with EWP and Combat Reflexes

Note that you can use the spiked chain for reach and attacks of opportunity, but you can't make a true tripper build because you lack strength and feats.

With two short swords, you don't have one hand free for infusions, scrolls and wands, so you might want to consider the quick draw feat.

If you don't want to use your feats for combat abilities and rather buff your artificing, just take the rapier.

Since you have proficiency with all martial weapons, don't forget to get a composite longbow appropriate for your strength. With your good dex and a quick infusion into your bow, you make a good backup archer.

Since we don't aim for anything except lots of Artificer levels, feats can pretty much be taken as desired.

For the spiked chain route, EWP spiked chain, Combat Reflexes, Combat Expertise, Improved Disarm are the feats of choice. Improved Trip could be a disappointment as you lack the strength to trip properly, and boosting your strength would take too many ressources.

Another option is Two-Weapon Fighting. Oversized TWF for two rapiers is not worth it, either go classic rapier and main-gauche (= dagger) or two short-swords.

If you only use rapier and buckler, don't waste feats on combat and improve your artificing.

Good options:

Practised spellcaster

brings your artificer spellcaster level back to maximum, and you could even squeeze in another 1 level dip, such as the Duelist PrC

Attune Magic Weapon

This is a must have. It's even worth going for Swashbucker 1 / Artificer 5 to take that feat at 6th level.

Daredevil Athlete

Well, you could also use an infusion to boost your skills, but you don't want to completely rely on them, right? This feat is nice for the swashbuckling flavor. (Complete Scoundrel)

Rapid Infusion

Necessary to boost your weapons and armor with infusions in combat without wasting an action point. (Magic of Eberron)

Extend Spell

A good high-level option. The all-important weapon and armor enhancement infusions last 10 minutes/level, spell-storing infusion lasts even 1 hour / level. Double that and you're prepared for several encounters with just one infusion. For example, at artificer level 15, an extended Weapon Augmentation lasts 300 minutes, that's 5 hours!

Extraordinary Artisan

Another must-have. Paying only 75% for items is like 1/3 more equipment.

Quicken Spell

Another excellent high-level option, although you don't get really high-level infusion slots

Remember that most of your infusions are just like standard spells, taking a standard action to cast (sorry, infuse). Only your most precious infusions, the ones that boost armor and weapons, take 1 minute to cast.

Personal Weapon Enhancement

The first, most important Infusion is Personal Weapon Enhancement, used to make the weapon a Bane weapon. +2 enhancement bonus and +2d6 bonus damage against one type of creature is really amazingly good for a 1st level infusion.

If Bane does not work because there are too many enemies of different types, try Keen (on a rapier or spiked chain) or Flaming. Ghost Touch comes handy against certain enemies.

With this infusion, you can also make a spell-storing weapon (note that this is different from the Spell-Storing Item infusion, which creates a "1-charge wand"). If you have enough time to prepare before an encounter, you can make your weapon spell-storing, and use a self-made scroll to charge it. Remember that with a good UMD you can make scrolls of pretty much any spell, so choose a nice melee or ranged touch attack spell of levels 1-3. Think about Poison, Vampiric Touch, Ghoul Touch and Scorching Ray.

Lesser Armor Enhancement

Probably the best use of this one is grant yourself or someone else a +5 bonus to Escape Artist, Hide or Move Silently. You can also glamer the heavy armors of your comrades when the group has to keep a low profile.

Armor Enhancement

The level 2 power is even better, as you can get Invulnerability (DR 5/magic). While this type of DR is easy to overcome for PCs and NPCs, it still protects against many monsters. This build aims for high AC, but DR is always a good backup. The other nice use of this infusion is making a shield animated.

Spell-Storing Item

Explaining the awesomeness that is the Spell-Storing Item infusion would take too long here, just google.

Of course, you want to make the artificer standards, such as a custom item that grants a bonus to Use Magic Device (probably goggles).

Basicly, don't buy but use all gold to make what you can make.

At 3rd level artificer, you can build Woundrous Items, the first chance to go crazy. Cheap basic items are

a cloak of resistance

gloves of Dexterity

an amulet of health or an amulet of natural armor

a bag of holding or a handy haversack

boots of striding and springing (replace by winged boots later)

circlet of persuasion helps with UMD and social skills (if you have them from your Swashbuckler levels)

efficient quiver

headband of intellect

Even if you find something better later you might still make a party comrade happy with them.

Also, feel free to make comparatively inexpensive items that don't have obvious combat value but could be useful in some situation, and are cheap enough. My personal favorite is the Cloak of the Manta Ray, in a campaign with lots of sea travel this thing owns.

The first goal we aim for is Swashbuckler 1/Artificer one. Starting as Swashbuckler is probably better because you get a full d10 hit points. Skill points are the same at 4+Int/level. Interestingly, the class skill lists of both classes are almost complementary, there is almost no skill on both lists.

What you want to get from your first Swashbuckler level:

Proficiency will all martial weapons

Tumble skill ranks (and Jump for Tumble synergy)

free Weapon Finesse

From your first Artificer level:

the ability to make and use scrolls

Use Magic Device skill ranks

your first infusions

After that, the next breakthrough points are both Artificer 3 (Craft Wondrous Item) and Swashbuckler 3 (Int bonus to damage). It depends on your personal taste which route you want to go first. After that, it's all Artificer.

You could even take Swashbuckler at first level, then 5 levels of Artificer until you have Craft Magic Weapons and Armor, and then stack up the missing to Swashbuckler levels.

As for feats, I've written above that there is no "best route", it depends on your choice of weapon.